This document is an introductory document on the topic of commonly used materials for reinforcement of concrete. This primer describes the basic properties and uses of these materials. It is targeted at those in the concrete industry not involved in designing with or specifying these materials. Students, craftsman, inspectors, and contractors may find this a valuable introduction to a complex topic. The document is not intended to be a state-of-the-art report, user's guide, or a technical discussion of past and present research findings on the subject.